Electrodeposition is a common technique for depositing material on a substrate. Electrodeposition generally involves applying a voltage to a substrate placed in an electrodeposition bath to reduce metal ionic species within the bath which deposit on the substrate in the form of a metal, or metal alloy, coating. The voltage may be applied between an anode and a cathode using a power supply. At least one of the anode or cathode may serve as the substrate to be coated. In some electrodeposition processes, the voltage may be applied as a complex waveform such as in pulse plating, alternating current plating, or reverse-pulse plating.
A variety of metal and metal alloy coatings may be deposited using electrodeposition. For example, metal alloy coatings can be based on two or more transition metals. Tungsten-based coatings are one example of an electrodeposited coating. Such coatings may be tungsten alloys including one or more of the elements Ni, Fe, Co, B, S and P. These coatings often exhibit desirable properties, including high hardness, abrasion resistance, good luster, wear properties, coefficient of friction in sliding applications, amongst others.
Generally, the electrodeposition baths include one or more metal sources as well as additives that may improve the deposition process and/or the resulting coating. The metal source(s) may be selected based on the desired composition of the metallic coating on the article. Typical additives include wetting agent(s), brightening agent(s), leveling agent(s), carrier(s), ductility agent(s), and others.
There is ongoing need for developments of new additives and/or new additive combinations to further improve the deposition process and/or the resulting coating. In particular, there is a need for new additives and/or new additive blends that are effective in electrodeposition processes that use complex waveforms such as in pulse plating, alternating current plating, or reverse-pulse plating.